Control stick transducer

ABSTRACT

A transducer for monitoring forces applied to an aircraft control stick includes a spring flexure which acts as a primary restraint to loads applied to the control stick. The spring flexure is secured to the transducer housing and disposed in a horizontal plane. The control stick handgrip is supported above the spring flexure by means of a vertical member passing through a central hub of the spring flexure so that the flexure provides a resilient mounting responsive to forces applied to the handgrip in any horizontal direction. A counterbalance suspended from the same hub of the flexure cancels the effect of any acceleration forces parallel to the spring flexure that may be induced in the mass of the handgrip and its mounting. Cantilevered load beams are arranged to deflect in response to loads applied to the handgrip in excess of an adjustable threshold value. Strain gauges are used to measure the deflection of the load beams and thus provide electrical output signals indicative of the amount of command force applied to the handgrip. Stop members limit the deflection of the spring flexure to values suitable for use with the strain gauges.

United States Patent Oliver [451 July 11, 1972 [54] CONTROL STICKTRANSDUCER Kenneth L. Oliver, Phoenix, Ariz.

[73] Assignee: Sperry Rand Corporation [22] Filed: May 10, 1971 [21]Appl. No.: 141,898

[72] Inventor:

[52] US. Cl. ..338/2, 244/83 E, 244/83 R [51] ..G0ll l/22 [58] FieldofSearch ..338/2, 3, 5; 244/83 E, 83 R; 73/133, 141 A [56] ReferencesCited UNITED STATES PATENTS 3,434,342 3/1969 Kazmarek ..73/l33 3,447,7666/1969 Palfreyman "338/5 X Primary ExaminerC. L. Albritton Attorney-S.C. Yeaton [57] ABSTRACT A transducer for monitoring forces applied to anaircraft control stick includes a spring flexure which acts as a primaryrestraint to loads applied to the control stick.

The spring flexure is secured to the transducer housing and disposed ina horizontal plane. The control stick handgrip is supported above thespring flexure by means of a vertical member passing through a centralhub of the spring flexure so that the flexure provides a resilientmounting responsive to forces applied to the handgrip in any horizontaldirection. A counterbalance suspended from the same hub of the flexurecancels the effect of any acceleration forces parallel to the springflexure that may be induced in the mass of the handgrip and itsmounting.

Cantilevered load beams are arranged to deflect in response to loadsapplied to the handgrip in excess of an adjustable threshold value.Strain gauges are used to measure the deflection of the load beams andthus provide electrical output signals indicative of the amount ofcommand force applied to the handgrip. Stop members limit the deflectionof the spring flexure to values suitable for use with the strain gauges.

8 Claims, 3 Drawing Figures Patented July 11, 1972 3,676,818

2 Sheets-Sheet 1 FlG.l.

.Z'N VEA/TOR KENNETH L. OLIVER gQ M/ M A T TOHNEY Patented July 11, 19722 Sheets-Sheet 2 INVENTOR K5 NETH L. OLIVER FIG.3.

Lyn M CONTROL STICK TRANSDUCER BACKGROUND OF THE INVENTION 1 Field ofthe Invention The invention relates to aircraft control devices and moreparticularly to aircraft control sticks providing an electrical outputsignal.

2. Description of the Prior Art Aircraft control sticks ordinarilyactuate the appropriate aircraft control surfaces through mechanicallinkages.

Patent Application Ser. No. 1 16,334 entitled Control Wheel ForceSensors, filed in my name and assigned to the present assignee concernsan aircraft control device which functions in cooperation with anaircraft control wheel to translate pilot-applied pitch and rollcommands into appropriate electrical output signals to control theaircraft attitude. Individual flexure springs deflect in response topitch and roll commands. The deflection of the flexures is detected andmeasured by a plurality of cantilevered load beams that actuateelectrical strain gauges. The cantilevered beams are firmly affixed tothe control column. The free ends of the cantilevered beams are actuatedby yoke members which move in response to deflection of the flexures.Each yoke member is adjusted to permit an initial movement beforecontacting the free end of the respective cantilevered beams, thuseffectively providing a predetermined dead zone. Adjustable stops limitthe maximum deflection of the flexures. The dead zone prevents initialdisplacements of the control wheel, such as those caused by the weightof the pilots hands, from affecting the strain gauges. The stops preventthe strain gauges from being subjected to excessive loads.

Although the invention of Ser. No. 1 16,334 provides a signiflcantadvance over the prior art, the method of mounting permits extraneousforces such as those induced by acceleration of the aircraft to affectthe output signal. This effect is particularly noticeable in relativelysmall, highly maneuverable aircraft. The present invention utilizes thedeflection sensing means of Ser. No. 116,334 but provides a mountingmeans that overcomes the effect of acceleration-induced forces.

SUMMARY OF THE INVENTION The present invention concerns an aircraftcontrol stick transducer which includes a primary spring flexurearranged to provide a virtual pivot point common to deflections in boththe longitudinal and lateral axes. The pivot point not only allows thehub of the flexure to move spherically and without friction in responseto any combination of pitch and roll commands, but also permits themechanism to be mass-balanced so as to overcome extraneousacceleration-induced forces.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an outline drawing of atypical control stick transducer of the type employing the principles ofthe invention,

FIG. 2 is a schematic drawing illustrating a sensor mechanism useful inpracticing the invention, and

FIG. 3 is a drawing illustrating a typical arrangement of componentsused in practicing the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a controlstick transducer of the type in which the present invention may be used.A control grip 11 is mounted to the transducer housing 13 by means of acoupling ring 15. The transducer housing, in turn, is mounted along theaxis 16 of the aircraft control column 17 by means of a coupling ring19. Pitch command signals are applied to the handgrip 11 by moving thegrip to the left or right to cause the craft to descend or ascend,respectively. Roll forces are applied in a direction normal to the planeof the paper in order to cause the craft to execute an appropriate rollmaneuver.

FIG. 2 illustrates a cantilevered beam sensing mechanism presentlypreferred for use with the invention. The sensing mechanism of FIG. 1 isessentially the same as that described in the aforementioned patentapplication.

In brief, this sensing mechanism includes a cantilevered load beam 21secured to a member 23 by means of mounting screws 25 and 27. Anelectrical strain gauge is mounted in the base 29 of the cantileveredload beam. A slotted yoke 31 is movable with respect to the member 23 inresponse to forces applied to the handgrip along an axis indicated bythe arrow. Adjustable screw arrangements 33 and 35 permit apredetermined amount of clearance to exist between the yoke 31 and acontacting ball 37 inserted in the cantilevered beam. As explained inthe aforementioned patent application, the clearance provided by theyoke and the cantilevered beam permits a small amount of motion to occurbefore the strain gauge indicates an applied force. This threshold actsas a dead zone which permits the strain gauge to operate in its optimumregion.

FIG. 3 illustrates the arrangement of the components in a typicaltransducer and depicts the transducer 13 of FIG. I with the front plateremoved to show the relationship of the various components within thetransducer housing.

The threaded coupling 39 mates with the coupling ring 15 of FIG. 1 inorder to attach the handgrip to the transducer housing. Similarly, athreaded coupling 41 permits the transducer housing to be secured to theaircraft control column.

The threaded couplings 39 and 41 may also support electrical connectorsfor coupling signals from the handgrip to the transducer or from thetransducer" to external electrical apparatus.

The threaded coupling 39 is part of a grip mount 43 which includes amechanical coupling section 45 attached integrally to a shaft 47. Theshaft 47 provides means for mounting cantilevered roll load beams 49,51, 53 and 55 as well as cantilevered pitch load beams 57, 59, 61 and63. The bases of the pitch load beams are located behind the pitch yokemembers 65 and 67 and the free ends of the beams extend into the yokemembers as depicted in FIG. 3. The base elements of the pitch load beamsare secured to the shaft member 47. The shaft member 47 also supports acounterbalance 69.

The entire movable assembly is supported by means of a spring flexure 71which is terminated in flange members 73 and 75 which are, in turn,secured to the housing by any suitable means such as bolt members 77,79, 81 and 83.

The spring flexure consists of compliant arms 85 and 87. The compliantarms preferably have a rectangular cross-section in which the width isseveral times the thickness of the arm. The arms may be formed from ahardened steel so as to be only slightly compliant in response toexpected command forces. The flexure member is disposed in a horizontalplane normal to the axis 16 of the control stick. With no command forcesapplied to the handgrip, the flexure remains in its quiescent conditionand the arms 85 and 87 remain fiat. A mounting hub 89 is formedintegrally with the compliant arms and supports the shaft 47 in a rigidrelationship with respect to the hub.

A pitch or roll command force applied to the handgrip causes thecompliant arms 85 and 87 to deflect so that the mounting hub 89effectively moves in a nutational fashion about a virtual pivot point91. Effectively, the mounting hub may move in a spherical manner withoutfriction since the only motion permissible is the motion provided by thedeflection of the compliant arms 85 and 87.

Slotted yokes 93 and 95 straddle the free ends of the cantilevered rollload beams and support adjusting screws for setting the dead band forthese load beams. The slotted yokes 93 and 95 are supported on theflanges 73 and 75, respectively. The yoke members 93 and 95 furthersupport the pitch yoke members 65 and 67, respectively.

Thus all yoke members, as well as the spring flexure itself, aresupported on the flange members 73 and 75. This arrangement is preferredin that it facilitates assembly and repair and That various straingauges mounted on the bases of the associated cantilevered beams respondto deflection of the beams whenever the motion of the shaft 47 issufficient to cause a beam to contact the associated yoke member.

In accordance with the teachings of the aforementioned patentapplication, the dead zone provided by the slotted yokes permits thestrain gauges to be operated in their most favorable regions.

Stop members 97 and 99 limit the motion of the movable portions of thetransducer by limiting the arcuate motion of the counterbalance 69 inresponse to pitch commands. Similarly, stop members are provided on theback plate and the front plate of the transducer housing (not shown) soas to contact either the mechanical coupling section 45 or thecounterbalance 69 when a predetermined maximum roll motion of thehandgrip 11 occurs.

Various elements in the transducer may be readily replaced if necessaryby virtue of the relatively simple arrangement of components.

The counterbalance 69 is selected and positioned on the shaft 47 toprovide a moment of inertia about the virtual pivot point 91 which isequal to the moment of inertia of the handgrip l1 and its mountingelements about the same pivot point. Thus acceleration forces induced inthe handgrip 11 because of aircraft maneuvering are balanced by theacceleration forces induced in the counterbalance 69 and its mountingsystem.

The electrical leads from the various strain gauges may be brought outthrough the lower threaded coupling 41 to exterior utilizationapparatus.

The transducer illustrated in FIG. 3 provides quadruple redundancy inboth the pitch and roll planes. It will be unde'rstood, however, thatany suitable degree of redundancy may be provided as described.

While the invention has been described in its preferred embodiment, itis to be understood that the words which have been used are words ofdescription rather than limitation and that changes may be made withinthe purview of the appended claims without departing from the true scopeand spirit of the invention in its broader aspects.

lclaim:

1. A transducer for an aircraft control stick comprising a springflexure means disposed in a plane normal to the axis of said controlstick, a handgrip on said control stick, a mounting hub on said springflexure, said mounting hub being constrained to nutational movementabout a pivot point by said spring flexure, means to mount said handgriprigidly on said hub, a counterbalance suspended from said hub so as tohave a moment of inertia equal to that of said handgrip, and means toprovide an electrical signal indicative of the amount of deflection ofsaid spring flexure.

2. The apparatus of claim 1 in which the means to mount the handgrip onsaid hub includes a shaft member secured in fixed relationship to saidhub, said shaft member extending beyond said hub on the side of saidspring flexure member pposite said handgrip, said counterbalance beingmounted on the extension of said shaft member.

3. The apparatus of claim 2 in which said transducer is enclosed in ahousing and wherein said flexure member includes mounting flanges forrigidly attaching said flexure member within said housing, said means tomount said handgrip being movable with respect to said housing, and stopmeans secured to the walls of said housing for limiting the nutationalmovement of said flexure.

4. The apparatus of claim 3 wherein said means to provide an electricalsignal includes cantilevered load beam means secured to said shaftmember, means to deflect said load beam means in response to nutationalmovements of said shaft and strain gauge means responsive to thedeflection of said cantilevered beam means.

5. The apparatus of claim 4 in which said cantilevered beam meansincludes a plurality of cantilevered beams, said apparatus furtherincluding slotted yoke means for actuating each cantilevered beam, saidyoke means being secured to said mounting flanges and arranged tostraddle the free ends of said cantilevered beams, said yoke means beingproportioned to provide a specified clearance between the yoke and thecantilevered beam when said flexure member is in its quiescent position.

6. The apparatus of claim 5 wherein said plurality of cantilevered beamsincludes a first group of beams arranged to de tect motion in responseto pitch forces applied to said handgrip and a second group of beamsarranged to detect motion in response to roll forces applied to saidhandgrip.

7. A control stick force transducer comprising a transducer housing,means to mount a handgrip on said transducer, means to mount saidtransducer on an aircraft control column, a spring flexure mounted insaid housing, a central mounting hub on said flexure resilientlysupported by a pair of radially disposed spring arms each having arectangular cross-section and lying in a plane normal to the axis ofsaid control column, a shaft secured to said mounting hub and supportingsaid handgrip above said flexure, said handgrip being free to movethroughout a limited range in response to roll and pitch forces appliedto said handgrip whereby said mounting hub is caused to deflect in aspherical fashion about a virtual pivot point, a counterbalance, saidshaft extending below said mounting hub and supporting saidcounterbalance at a distance below said pivot point that provides amoment of inertia equal to that of said handgrip with respect to axeslying in said normal plane, stop means to limit the deflection of saidspring flexure, and electrical sensing means to provide signalsindicative of the amount of deflection of said spring flexure.

8. The apparatus of claim 7 wherein said sensing means includescantilevered beams arranged to be deflected in response to motions ofsaid shaft in excess of a predetermined threshold, said cantileveredbeams having a compliance much greater than the compliance of saidspring flexure, and wherein said electrical sensing means includesstrain gauge means arranged to respond to deflections of saidcantilevered beams.

1. A transducer for an aircraft control stick comprising a springflexure means disposed in a plane normal to the axis of said controlstick, a handgrip on said control stick, a mounting hub on said springflexure, said mounting hub beIng constrained to nutational movementabout a pivot point by said spring flexure, means to mount said handgriprigidly on said hub, a counterbalance suspended from said hub so as tohave a moment of inertia equal to that of said handgrip, and means toprovide an electrical signal indicative of the amount of deflection ofsaid spring flexure.
 2. The apparatus of claim 1 in which the means tomount the handgrip on said hub includes a shaft member secured in fixedrelationship to said hub, said shaft member extending beyond said hub onthe side of said spring flexure member opposite said handgrip, saidcounterbalance being mounted on the extension of said shaft member. 3.The apparatus of claim 2 in which said transducer is enclosed in ahousing and wherein said flexure member includes mounting flanges forrigidly attaching said flexure member within said housing, said means tomount said handgrip being movable with respect to said housing, and stopmeans secured to the walls of said housing for limiting the nutationalmovement of said flexure.
 4. The apparatus of claim 3 wherein said meansto provide an electrical signal includes cantilevered load beam meanssecured to said shaft member, means to deflect said load beam means inresponse to nutational movements of said shaft and strain gauge meansresponsive to the deflection of said cantilevered beam means.
 5. Theapparatus of claim 4 in which said cantilevered beam means includes aplurality of cantilevered beams, said apparatus further includingslotted yoke means for actuating each cantilevered beam, said yoke meansbeing secured to said mounting flanges and arranged to straddle the freeends of said cantilevered beams, said yoke means being proportioned toprovide a specified clearance between the yoke and the cantilevered beamwhen said flexure member is in its quiescent position.
 6. The apparatusof claim 5 wherein said plurality of cantilevered beams includes a firstgroup of beams arranged to detect motion in response to pitch forcesapplied to said handgrip and a second group of beams arranged to detectmotion in response to roll forces applied to said handgrip.
 7. A controlstick force transducer comprising a transducer housing, means to mount ahandgrip on said transducer, means to mount said transducer on anaircraft control column, a spring flexure mounted in said housing, acentral mounting hub on said flexure resiliently supported by a pair ofradially disposed spring arms each having a rectangular cross-sectionand lying in a plane normal to the axis of said control column, a shaftsecured to said mounting hub and supporting said handgrip above saidflexure, said handgrip being free to move throughout a limited range inresponse to roll and pitch forces applied to said handgrip whereby saidmounting hub is caused to deflect in a spherical fashion about a virtualpivot point, a counterbalance, said shaft extending below said mountinghub and supporting said counterbalance at a distance below said pivotpoint that provides a moment of inertia equal to that of said handgripwith respect to axes lying in said normal plane, stop means to limit thedeflection of said spring flexure, and electrical sensing means toprovide signals indicative of the amount of deflection of said springflexure.
 8. The apparatus of claim 7 wherein said sensing means includescantilevered beams arranged to be deflected in response to motions ofsaid shaft in excess of a predetermined threshold, said cantileveredbeams having a compliance much greater than the compliance of saidspring flexure, and wherein said electrical sensing means includesstrain gauge means arranged to respond to deflections of saidcantilevered beams.